1. Field of the Invention
The present invention relates to an optical parametric amplifier (OPA). In particular, the present invention relates to providing the blue light and the near-ultra-violet (380–460 nm) a continuously tunable optical parametric amplifier by using cascaded sum frequency generation of femtosecond non-collinear optical parametric amplifier.
2. Description of Relative Prior Art
In the near decade, the applications of the blue light become more important. The most important industry is high intensity storage. This wave length is very important for the application of bio-technology and environment control areas. Moreover, in the application of time-resolved and frequency-resolved studies, real time studies of molecular dynamical and optical spectrum studies, show that the development potential of the blue light and near-ultra-violet radiation. However, the source and the detector of the blue light and the near-ultra-violet light is still not enough. In the near decade, due to the development of non-linear crystal and laser technology is more come to mature, this makes possible of the tunable wave-length optical source of this wave-band. The trend is to generate a higher quality and convenient source and to increase the efficiency.
Optical parametric amplifier (OPA) is an important means to generate tunable-wavelength. But it is very difficult to generate blue light directly from the OPA. Generally, it needs to go through another non-linear optical process, such as frequency doubling or sum frequency generation, which increases the complexity and cost.
In the published documents, such as in the articles “ultra fast optical parametric amplifiers”, Giolio cerallo et al., Review of scientific Instruments 74, 1–17(2003), relates to the generation of tunable wave-length optical source by OPA process; In the article “Generation and amplification of ultra-short shaped pulses in the visible by a two-stage non-collinear optical parametric process”, Howe-Siang et al., Opt. Lett. 26, 1812–1814(2001); and “Broadband optical parametric amplification in the near UV-VIS”, Tzankov et al., Opt. Commum., 2003, 107˜(2002); “Broadband amplification of ultraviolet laser pulse”, Osvay et al., Appl. Phys. B: Lasers Opt. B74, S163-2002(2002); emphasized by summing the frequency of the generating long wave-length. This makes the system more complex, and that summing frequency process itself also has time overlap problem, the output is not stable due to mechanical problem. In the article “Extension of tuning range of a femtosecond Ti: sapphire laser amplifier through cascaded second-order nonlinear frequency conversion process”, Petro et al., J. Appl. Phys, 76, 7704–7712(1994); the designed architecture is based on the last stage of photo-frequency mixing or sum frequency generation, which is different from the article “Generation of femtosecond laser pulses tunable from 380 nm to 465 nm via cascaded nonlinear optical mixing in a non-collinear optical parametric amplifier with a type-1 phase matched BBO crystal”, chao-Kuei lee et al., Opt Express 11,1702–1708(2003), this article makes use of a cascaded non-linear Optical mixing to generate tunable-wavelength of femtosecond non-collinear optical parametric amplifier.
In the U.S. Pat. No.5,144,629 to basu ; U.S. Pat. No.5,751,472 to jeys et.al., and U.S. Pat. No.5,769,513 to Stamm et.al., are implemented general optical parametric amplifier architecture, and only has signal and idler output.
The prior art of optical parametric amplifier with blue light out put basically is by using the output of generated long wave-length to generate the necessary short wave-length by sum-frequency, or by using high-order harmonic to generate excited light source of shorter wave-length. The disadvantage is that the wave length of the excited light source generation is not easy because of the transformed efficiency of high-order harmonic is low, group velocity mismatched, short wave-length thin-film deposition is not easy, and high cost. The last stage of optical mixing or sum-frequency architecture makes the system more complex, which is not convenient and limited in application consideration.
What is needed is an improved tunable wave-length femtosecond non-collinear optical parametric amplifier.